Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$88.69	13.250%	$100.4414	$100.44	$100.45	$100.40
Purchase #2	$160.72	10.472%	$177.5506	$177.55	$177.55	$177.60
Purchase #3	$223.28	6.630%	$238.0835	$238.08	$238.10	$238.10
Purchase #4	$49.96	5.134%	$52.5249	$52.52	$52.50	$52.50
Purchase #5	$144.41	8.716%	$156.9968	$157.00	$157.00	$157.00
Purchase #6	$185.81	8.103%	$200.8662	$200.87	$200.85	$200.90
Purchase #7	$52.95	11.517%	$59.0483	$59.05	$59.05	$59.00
7 purchase totals =	$905.82		$985.5117	$985.51	$985.50	$985.50